"Mulching" mowers are known which deposit or hide the grass clippings in the cut grass path as opposed to simply discharging such clippings on top of the grass or collecting the clippings in some type of bagging apparatus. Such mowers vary widely in their ability to actually hide the clippings with some mowers doing a better job than other mowers. However, the term "mulching" when used to describe a mower generally refers to a mower which is intended to deposit the clippings in the cut grass path, regardless of the degree of effectiveness such a mower might have.
So called "dedicated" mulchers are mowers designed only for this purpose as shown in U.S. Pat. No. 4,205,512 to Thorud. They generally have included a cutting chamber which is enclosed over the sides and top thereof and which is open only at the bottom. This allows the grass clippings cut by the blade to be deposited downwardly through the open bottom of the cutting chamber. In some cases, a specially shaped blade assists in the downward movement of the grass clippings, or grass deflector members may be carried inside the cutting chamber.
Interest has recently grown in the use of mulching mowers particularly with the advent of restrictions by municipalities on the disposal of yard waste in landfills. To that end, The Toro Company, the assignee of the present invention, has designed and introduced a line of walk-behind mowers, known as Recycler.RTM. mowers. The Recycler.RTM. mowers are selectively convertible by the user between grass discharging, grass bagging, and grass mulching modes. In addition, these mowers include a plurality of grass deflecting members, also known as kicker members, which intercept the grass clippings circulating inside the housing to assist in their downward discharge from the cutting chamber when the mower is being used as a mulcher. U.S. Pat. No. 4,951,449 to Thorud illustrates a Recycler.RTM. mower.
Most rotary mowers, including those used for mulching, usually have cutting chambers which are circular, i.e. a chamber in which the cutting blade is centered within the chamber and the tip of the cutting blade maintains a constant nominal clearance to the wall of the cutting chamber at least within the manufacturing tolerances that are applicable. However, certain mowers have been designed with slightly non-circular or "obround" cutting chambers. The word "obround" is meant to refer herein to a cutting chamber which is not perfectly circular with respect to the blade tip. While an oval or elliptical chamber would also be an obround chamber, the word obround is meant to cover more than an oval or elliptical chamber. Thus, an "obround" chamber will mean any chamber in which the chamber has been stretched or elongated somehow with respect to a centered blade, or in which the blade has been offset relative to the center of a circular chamber, so that at least a portion of the chamber wall is farther away from the blade tip than the remaining portion of the chamber.
In the obround mowers known to Applicants, the obround portion was located in the front of the cutting chamber taken with reference to the direction of advance or forward motion of the mower, i.e. in that portion of the cutting chamber which first contacts the grass as the mower is moved forwardly. It was thought that this extra clearance between the blade and the front chamber wall would allow the uncut grass stems to be better lifted and elevated by the sail configuration on the blade before being cut. In other words, it was thought that the grass would be stood up better and thus be more uniformly cut with an obround portion in the front of the cutting chamber. The Toro Company has previously used such an obround portion in the front of the cutting chamber in certain of its products such as the Toro Grassmaster, Toro VDM Rear Bagger and Toro 21" Recycler.RTM..